Thermoplastic films for soil treatment

Abstract

Thermoplastic films comprising laminates of polyolefin and a relatively thinner polyamide layer are employed as protective coverings over agricultural fields, which have been treated with fumigants. The improved resistance to fumigant vapor penetration of such laminates results in improved retention of the volatile fumigant materials in contact with the soil which is being treated.

I claim: 
     
       1. A method for maintaining volatile agricultural fumigants in intimate contact with soil which comprises injecting soil fumigants into said soil and subsequently covering the fumigant treated soil with a laminar film comprising a polyolefin layer having adhered to the surface thereof a polyamide coating layer. 
     
     
       2. The method of claim 1 wherein said soil is injected with a fumigant selected from the group consisting of methyl bromide, chloropicrin and a mixed fumigant thereof. 
     
     
       3. The method of claim 1 wherein said polyamide is a nylon and said polyolefin is a polyethylene. 
     
     
       4. The method of claim 3 wherein the film has a substantially uniform overall thickness of about 0.5 to 3 mils. 
     
     
       5. The method of claim 4 wherein the nylon comprises no more than 20% of the overal thickness. 
     
     
       6. The method of claim 5 wherein the nylon is nylon-6 and the polyethylene is of a member selected from the group consisting of a high density homopolymer, a low density homopolymer, a high density copolymer with an alpha olefin and a low density copolymer with an alpha olefin. 
     
     
       7. The method of claim 6 wherein the polyethylene contains a minor adhesion promoting amount of an ionomer resin blended therein. 
     
     
       8. A method of fumigating soil comprising the steps of treating soil with an effective amount of a diffusion fumigant; covering the fumigant-treated soil with a multilayer gas barrier film comprising a polyamide layer and a polyolefin layer; and permitting the fumigant to diffuse through the covered soil. 
     
     
       9. The method of claim 8 wherein said fumigant is a member of the group consisting of methyl bromide, chloropicrin, and a mixed fumigant thereof. 
     
     
       10. The method of claim 8 wherein said polyamide comprises a nylon and said polyolefin is a polyethylene. 
     
     
       11. The method of claim 10 wherein the film has a substantial overall thickness of about 0.5 to 3 mils. 
     
     
       12. The method of claim 11 wherein the nylon comprises no more than 20% of the overall thickness. 
     
     
       13. The method of claim 12 wherein the nylon is nylon-6 and the polyethylene is of a member selected from the group consisting of a high density homopolymer, a low density homopolymer, a high density copolymer with an alpha olefin and a low density copolymer with an alphaolefin. 
     
     
       14. The method of claim 13 wherein the polyethylene contains a minor adhesion prompting amount of an ionomer resin blended therein.